In the latest Drought Monitor update, drought conditions have improved almost everywhere in the United States except for Florida. In the 17 year history of the Drought Monitor index, the drought outlook has never been better with less than 5% of the country under a drought classification. The last time the Drought Monitor looked this good was July 2010.

The U.S. Drought Monitor is produced through a partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.

An intense storm developed over the central Plains and moved through the Midwest last week, bringing with it torrential rains and thunderstorms on the front side and heavy, wet snow on the back side. A wide swath of the country from eastern Oklahoma through Arkansas, Missouri and into Illinois recorded over 5 inches of rain with the event. Portions of western Kansas and the Oklahoma Panhandle recorded several inches of snow, with some places over a foot. The Southeast remained dry as well as much of the Southwest.

Heavy rain that fell over portions of the Mid Atlantic and Northeast yesterday will help squash flood concerns there.

Unfortunately, conditions continue to get worse for the Sunshine State. Florida is living up to its nickname, with more sunshine than rain. The end result is an Extreme Drought classification for portions of central Florida. Georgia still has drought issues too; the northern part of the state is seeing Extreme Drought too.
The dry conditions in Florida are creating significant fire issues. The Florida Forest Service reports there are more than 1,900 active fires in the state consuming thousands of acres of land.
In the current weather pattern, no relief is expected for the southeast in the short-term.

Map shows incredible warmth over a one week period during February 2017. Image Credit: High Plains Regional Climate Center

Meteorologists look at weather patterns around the globe to help determine short and medium range forecasts; one such pattern explored is the Bering Sea Rule, and it suggests that incredible warmth will return to much of the United States come mid-March. The unusual warm weather could also be joined by another severe weather outbreak.

Joseph Renken, who developed a long-range forecasting tool called the Bering Sea Rule (BSR), believes current signals suggest a wild and warm March. “Severe thunderstorms look likely on the tenth and eleventh of the month from the central Plains, eastward into the Mississippi and Ohio Valleys and extending into the mid-Atlantic region.” Renken further explained, “A low pressure system will form over the lee of the Rockies and over the Plains of Colorado, and will head east-northeastward. Its associated cold front will push into the Plains and head eastward and will be the cause of this severe weather outbreak.” Renken believes the pattern setting up won’t just create one severe weather outbreak. “Even though climatologically-normal temperatures are rising very fast in the middle of the month, we can expect temperature departures to be in the 10-20 degrees above normal range across much of the central and eastern U.S., which are very similar departures to what the same area of the country saw over the mid and late part of February.”

Renken believes that another anomalous warm spell that could rival February’s is possible. “Around the 27th of February, the combination of high pressure just to the south of Kodiak Island and a strong storm between Attu Island and the Kamchatka peninsula will exaggerate the ridging over the east Aleutian Island chain. Another storm a few days later, as the calendar flips to March, near the Sea of Oshkosh, will cause the ridge to become even stronger and to be forced westward. With the 18-day lag that the BSR is currently showing, this ridge should teleconnect to a strong ridge over the central part of the U.S. starting around the 14th of March.”

These maps produced by Joseph Renken and his BSR team overlay a map of the continental United States onto a National Weather Service Weather Prediction Center Pacific map.

If the forecast comes to fruition, such a ridge over the central US will be associated with incredible warmth. Temperatures in the 80s and even 90s will be common for much of the southern and central Plains as well as the adjacent Mississippi valley region. Renken adds that the configuration of this warm air mass will be slightly different, which could have implications for New England. “There is a difference between this upcoming ridge and the one that was associated with all the warmth of the past few weeks as it will be centered a bit further to the west. This will leave the Northeast, particularly New England, more at risk of some backdoor cold fronts that will hold back the warming the more northeast one is.” But with lack of snowcover, anomalously warm southern Canada, and a gradually higher warming sun angle, cold shots for New England likely won’t be too long nor too harsh. “It should only be a matter of time until the warmth from the ridge across the central US is pushed eastward thanks to a continued unusually strong Pacific jet. So while New England may be cooler longer, they too will warm.”, Renken said.

That strong Pacific jet and atmospheric rivers of moisture have blasted the US west coast, especially California, with heavy rain; this evolving weather pattern may help California dry out a bit in March, albeit briefly. As the Pacific jet weakens somewhat, the first part of March will allow places like California to recover from recent heavy, record-breaking precipitation. However, as the Bering Sea ridge weakens, the Pacific Jet will become active again Renken expanded: “The Pacific jet has incorrectly been described as part of the ‘Pineapple Express’ this winter. Generally this winter, that description has been inaccurate. California has been dumped on not because of moisture from the tropics, such as the Pineapple Express, but simply because the strength and persistence of the west to east flow across the Pacific has picked up oceanic moisture that it is forced to drop once it encounters the Sierra Nevadas.” Don’t put away the umbrellas and snow shovels yet. “As the central ridge flexes its muscles in a few weeks, the Pacific jet will yet again lengthen and strengthen. And its aim will continue to be on the Sierra Nevadas of California.” With heavy precipitation returning by mid-March, drought conditions will be further eliminated while threats of floods and other heavy-precipitation-related disasters mount.

Illustration by the Sacramento office of the National Weather Service illustrates the area around the Oroville Dam that could fail.

Roughly 190,000 have been evacuated below the Lake Oroville Dam in California as an emergency, auxiliary spillway shows signs of failure. With experts at the dam expecting an imminent failure of the spillway area Sunday evening, evacuations were ordered as the output of the dam was increased to 100,000 cubic feet per second to alleviate the surplus of water that exists in the lake.

The increased release appears to have prevented additional water from topping the spillway, but the danger of failure remains. As a result of the ongoing failure risk, evacuation orders remain up for the area near the dam.

“The situation has been stressful,” said Mark Ghilarducci, director of the state Office of Emergency Services. “It’s complex and rapidly changing, so we are doing everything we can to support Butte County and the local authorities to be able to address most of the folks who have been displaced.”

California Governor Jerry Brown released a statement Sunday evening after the evacuation order was issued by local authorities. “I’ve been in close contact with emergency personnel managing the situation in Oroville throughout the weekend, and it’s clear the circumstances are complex and rapidly changing,” Brown said. “I want to thank local and state law enforcement for leading evacuation efforts and doing their part to keep residents safe. The state is directing all necessary personnel and resources to deal with this very serious situation.”

The 7-day outlook from the National Weather Service’s Weather Prediction Center shows more heavy precipitation will be impacting California in the coming days, including the area around the Oroville dam crisis.

While it appears the auxilliary spillway may be stable at the moment, the weather forecast shows more trouble is in store for the state that has been rocked all winter by heavy rain and snow.

The 7-day outlook from the National Weather Service’s Weather Prediction Center shows more heavy precipitation will impact northern California. The liquid equivalent of 6-7″ of rain and snow is forecast to fall which will put incredible strain on the fragile situation around Lake Oroville.

There is currently 40,000 cubic feet of water arriving into the lake each second now and additional storms will lead to an exponential increase in that flow. Levees downstream the dam can handle flows of up to 150,000 cubic feet per second before flooding, but with the spillway of the dam compromised and more water rushing in, it may not be possible to hold back the increased flow from increased precipitation.

The Sacramento Bee spoke with Joe Countryman, a member of the Central Valley Flood Protection Board and a former engineer with the U.S. Army Corps of Engineers for context on the engineering issues in the Oroville Dam crisis. When asked about what a failure of the spillway meant, he told them, “It’s not going to be the main embankment failure, but it’s a failure. If it does happen, there’s nothing saying that the ground is going to stay where it is. That force of water will start tearing that hill apart, and it could eat back into the reservoir and drain the reservoir.”

If such a failure does occur, the cities of Marysville, Oroville, Live Oak, and the Highway 70 corridor are at extreme risk. Countryman warns about the area, “That’s gone. I’ll tell you right now that’s gone. If they lose that 30 feet that’s gone”, suggesting the Highway 70 corridor and surrounding communities would be wiped out by the breach.

The Oroville Dam was built in the 1960s; it is an earthfill embankment dam on the Feather River east of the city of Oroville. At 770 feet high, it is the tallest dam in the US and serves mainly for water supply, hydroelectricity generation and flood control. The dam holds back Lake Oroville, the second largest man-made lake in the state of California.

The U.S. Drought Monitor is produced through a partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.

A plume of moisture arriving from the central Pacific, known by some as the “Pineapple Express”, is bringing incredible moisture to drought areas of the west. California, especially central/southern portions of the state, is in a severe drought, the result of a string of rainy seasons that did not produce the normal amount of precipitation. Agriculture has suffered and water rationing and bans have been put into place, especially in the Los Angeles and San Diego regions. A strong El-Nino brought slightly wetter than normal conditions last winter but did not come close to alleviating the long term drought situation. So far this winter has been a blockbuster in terms of mountain snow and low elevation rain for northern and central California. Currently the Sierra Nevada mountain range is experiencing a winter storm where more than five feet of snow will fall on top of five feet that has already accumulated.

Some impressive rain amounts from the base of the Sierra Nevadas in a 24 hour period ending at noon Wednesday include 3.56 inches in Chilkoot Meadow, 3.17 inches at Beartrap Meadow, 2.63 inches at Shaver Lake and 2.44 inches at Fish Camp.

Snow amounts have been equally impressive. As of noon Wednesdaym Northstar at Tahoe reported 42 inches of new snowfall in the previous 24 hours, 78 inches in the previous 48 hours, and a whopping one week total of 122 inches. Mammoth Mountain reported a storm total snowfall of 116 inches and 1 week total of almost 180 inches. Kirkwood Ski Resort has seen 48 inches of new snow, 71 inches in the past 2 days and 133 inches in the last 7 days.

This strong winter storm is a result of a weather pattern called the “Pineapple Express.” According to long range meteorologist David Samuhel, “The jet stream across the North Pacific has been strong this year. It has been much stronger, in fact, than recent years. Part of the reason is the water temperatures profile of the central and eastern Pacific. The water temperatures have cooled across much of the North Pacific. While, water temperatures are warmer further south towards the Hawaiian Islands. Jet streams thrive in the zone between warm and cold. So, this normal pattern is strengthening with warmer than normal water south of the Pacific Jet and colder than normal water to the north.”

GOES water vapor satellite view taken on January 11. Courtesy of NOAA.

This stronger than normal jet stream moves overhead the warm waters near Hawaii and heads just south of the cooler waters in the North Pacific. Because the jet stream originates from the tropics, it is loaded with deep tropical moisture and we get storms such as this one that are loaded with Pacific moisture. With its origins near Hawaii, this weather pattern and associated string of storms gets the moniker of the “Pineapple Express”.

Many of the mountains that make up the Sierra Nevadas have well over their normal snow water equivalent to date, some approaching or exceeding double their normal amount. Snow water equivalent is defined as the amount of water being stored in the snowpack.

According to seasonal energy and agriculture forecaster Ed Vallee, “An active Pacific Jet has increased the storm track across the west leading to ample precipitation. This regime looks to continue across the West through the end of January.” This will continue to allow the drought situation to improve as the snowpack continues to buildup and rain falls along the coast and at lower elevations. Unlike the East when most areas see rain all four of their seasons, California experiences almost all of their precipitation between November and March. Thus the melting snowpack from the mountains is the main source of water for drinking and agriculture during the warm months. Though the Sierra Nevadas are hundreds of miles away from both Los Angeles and San Diego, their water is one of two main sources of their water supply; the second is the Colorado River. Mr. Vallee adds, “After years of drought, this pattern should positively benefit the region’s water supply through the spring.” The quenching weather pattern may not last. “As we move into February we expect this pattern to shift drier. Even so, occasional storms will continue to impact the region,” says Mr. Vallee.

Though the total area covered by snow is actually somewhat less this year as compared to last, the Sierra Nevadas have deeper snow and the snow extends further down the mountains into lower elevations, especially after this ongoing blizzard. In some cases, the snow is much deeper. The deeper snow more than compensates for the slightly lower coverage area-wise. This is because the main source for water during the warmer months is the Sierra Nevadas, as the lesser mountains have much less snow during the winter and it melts off before it is needed.

The drought situation is thus slightly improved since this rainy season started out so well and the snowpack is being built up nicely. What additional impacts this pattern has to the long term drought crisis in southern and central California is yet to be seen.